Carrier current amplifier apparatus



Sept. 1, 1942. P. Du MONT 2,294,735

CARRIER CURRENT AMPLIFIER APPARATUS Filed Aug. 23, 1939 mgl.

Paul du Mont.

His Attorney.

Patented Sept. 1, 1942 UNTD T ENCE Paul du Mont, Berlin-Spandau,

Germany, assignor to General Electric Company, a corporation of New York application August 23, 1939, Serial No. 291,601 In Germany September 5, 1938 (ci. 177-352)y 8 Claims.

This invention relates to apparatus for transmitting signals over power lines by carrier current and more particularly to carrier current apparatus for use in connection with a power system having at least two parallel sets of conductors feeding energy from or to power stations or substations.

An object of my invention is to provide a system for connecting a carrier current amplier to such a power system in a way which minimizes possibility of back coupling between the output and input circuits of such an amplifier. In carrying out my invention, instead of connecting the carrier currentl apparatus between two different phases of a power line, as had been previously done, I connect the apparatus between corresponding conductors of two parallel sets of conductors of the same phase. I also provide blocking means at suitable points in the power system to prevent the flow of carrier current in undesired parts of the system.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, however,

both as to its organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 illustrates an embodiment of my invention, and Figure 2 illustrates a modification of the apparatus shown in Figure l.

A power station or substation, indicated in Figure 1 as being enclosed by a rectangle I, is connected to a rst remote station by two parallel sets of 3 phase conductors. The rst set includes conductors II, I2, and I3, and the second set includes conductors I4, I 5 and I6. A second remote station, which is represented asv lying in the opposite direction, is also connected to station I 0 by two parallel sets of three phase conductors, of which the rst set includes conductors I'I, I8 and I9, and the second set includes conductors 20, 2I and 22. Within the station IIJ there are bus bars 23, 24, and 25, which interconnect the four sets of three phase conductors so that electrical power may ow therebetween.

Voltages of carrier frequency, which are impressed across conductors II and I4 at the iirst remote station are received by an amplifier 26 having its input terminals connected to conductors II and I4. Blocking means 2, which is indicated as comprising an inductance, is interposed in conductor II near the bus bar 23 and blocking means 28 is similarly interposed in coninput terminals of the amplifier.

ductor I4. The blocking means 2l and 28 are designed to have a very low impedance for power current, which is normally of much lower frequency than carrier curent and to have a high impedance for current of carrier frequency, so that such current will not be to any substantial extent short circuited through the bus bar 23 to which the conductors II and III are connected.

A pair of blocking means 29 and Si) are interposed respectively in the conductors I s and 22 of the sets of conductors leading to the second remote station` These conductors I9 and 22 form part of a diiTerent phase of the system than that upon which the incoming signals are impressed. The output terminals of the amplier 2E are connected to the conductors I9 and 22, so that a potential of carrier frequency produced by the amplier 26 is supplied for transmission to the second remote station. The blocking means 29 and 3i) prevent this potential of carrier frequency from being short circuited to any substantial extent through the bus bar 25 to which the ccnductors I9 and 22 are connected.

IThe conguration of the carrier and power circuits is especially arranged to minimize back coupling between the output and the input circuits of the amplifier 26, so that oscillation is prevented. Any carrier potentials which pass the blocking means 27 and 28 are short circuited by the bus bar Z3, and are thus prevented from affecting the output terminals of the amplifier 26, and similarly, carrier potentials which pass the blocking means 29 and 36 are short circuited by the bu-S bar 25 and prevented from affecting the There are, of course, capacitances between the various -phase conductors of the different sets of power lines. The dotted lines at 3| represent the capacity between conductors II and I2, and the dotted lines at 32 represent the capacity II and I3. Likewise the`dotted lines at 33 and 34 represent like capacities between conductor I4, and conductors I5 and I6 respectively. The capacities between the conductors extending to the secondl remote station are similarly represented by dotted line capacitances 35, I-i, Ill and which exist respectively between conductors I8 and Iii. I1 and I9, 2| and 22, and 2d and 22. Potentials of carrier frequency are cf course induced upon conductors I2, I3, I5 and Iii through the associated capacities, but since these capacities are of substantially equal value, the corresponding voltages are approximately balanced and are short circuited bythe busl bars 24 and 25. Similar voltages of carrier frequency are inbetween conductors duced on conductors I1, I8, 20, and 2|, and these voltages are likewise short circuited by the bus bars 23 and 24. An effective repeating amplifier for carrier current systems is thus provided. It is, of course, to be understood that the input and output of amplifier 2E may be transposed without altering the effectiveness of the scheme or the way in which it operates.

In Fig. 2 many elements are illustrated which are identical with those of Fig. 1 and these elements are given like reference characters. The conductors II, I2, and I3 are shown as extending only from the first remote station to the bus bars 23, 24 and 25. There is only the one set of conductors 20, 2|, and 22 leading to the second remote station. The connections of the amplifier 26 to the conductors II and I4 are exactly the same as in Fig. 1. The output terminals of the amplifier are connected to the conductors 2I and 22, since only one set of conductors is used. Since conductor 20 is connected to the bus bar 23 and thence to conductors II and I4, which carry the incoming signal, the amplified signal is applied between conductors 2I and 22 to minimize the possibility of cuit. Blocking means 39 and 40 are interposed in conductors 2| and 22 between the bus bars 24 and 25 and the connections to the amplifier 26 to prevent any substantial amount of voltage of carrier frequency from being transmitted to the bus bars.

Since this configuration of circuit elements produces carrier voltages which are substantially balanced with respect to amplifier input and output, the coupling therebetween is minimized with this circuit as well as with the circuit of Figure 1. It is, of course, clear that the repeating amplifier 26 may be constructed toA amplify in either or both directions. It is equally clear that if the amplifier 26 amplifies signals from conductors 2I and 22 and transmits them to conductors II and I4, there will be less possibility of back coupling than if signals are transmitted in the reverse direction. This is tnue since it is the output which affects the input and when the output is connected to conductors II and I4, any potential which passes the blocking means 21 and 28 is short circuited by the bus bar 23 so that it cannot affect the input.

While I have shown only two particular embodiments of my invention, it will, of course, be understood that I do not, wish to be limited thereto, since different modifications may be made both in the ycircuit arrangement and instrumentalities employed, and I aim by the -appended claims to cover any such modifications as fall within the tnue spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a power distribution system having two parallel conductors extending between substantially the same two geographically spaced points, means comprising a carrier current apparatus connected between said parallel conductors at one of said `points for transmitting current of carrier frequency through said conductors to the other of said points, means at said one point connecting said conductors to maintain them at the same potential for current of power frequency and forming a shunt path around said apparatus, and means in said shunt path for reducing the transmission of current of carrier frequency therethrough without substantially reducmg the transmission of power current, said back coupling in this cirlast means being in a portion of said shunt path not including any portion of said conductors carrying =current of carrier frequency to said other point, whereby said last means does not interfere with transmission of carrier current between said points.

2. In a :power distribution system having a plurality of parallel sets of conductors extending between substantially the same two geographically spaced points and a bus bar at one of said ipoints :connected between a conductor in one of said sets .and a corresponding conductor in another of said sets, means comprising carrier current .apparatus at said one point connected between said two corresponding conductors for transmitting current of carrier frequency through said two .conductors to the other of said points, said ,bus bar being arranged to maintain said lconductors at the same potential for current of power frequency and lying in a shunt path around said apparatus, and means in said shunt path for reducing the transmission of current of carrier frequency therethrough without substantially reducing the transmission of @power current, said last means being in a portion of said shunt path not including any portion of said conductors carrying current of carrier frequency to said other point, whereby said last means does not interfere with transmission of carrier current between said points.

3. A power distribution system havin-g a plurality of parallel sets of conductors extending between substantially the same two geographically spaced :points and a bus bar at one of said points `connected between a conductor in one of said sets and a corresponding conductor in another of said sets, means for transmitting current of carrier frequency through said two conductors between said points, said means comprising a I,carrier current amplifier at said one point having its input circuit connected between said two corresponding conductors, s aid bus bar being arranged to maintain said two conductors at the same potential for current of power frequency and lying in a shunt path around said input circuit, and means in said shunt path for reducing the transmission of currents of carrier frequency therethrough without substantially reducing the transmission of power current, said last means .being in a portion of said shunt path not including any portion of said conductors carrying current of carrier frequency between said points to said input circuit, whereby said last means does not interfere with transmission of carrier current between said poin 4. In a power distribution system having a plurality of parallel sets of conductors extending between substantially the same two geographically spaced points and from one of said points to a third point, and bus bars at said one point, each of said bus bars being connected between a conductor in one set and a corresponding conductor in another set of said conductors, means for transmitting current of carrier frequency through said conductors from the other of said two points to said third point, said means comprising a carrier current amplifier at said one point having its input circuit connected in shunt to one of said bus bars and its output circuit connected in shunt to another of said bus bars, said bus bars lying in respective shunt paths around the input and output circuits of said amplifier, and means in each of said shunt paths for reducing the transmission of currents of carrier frequency therethrough without substantially reducing the rality of parallel sets of conductors extending between substantially the same two geographically spaced points and from one of said points to a third point, and bus bars at said one point, each of said bus bars being connected between a conductor in one set and a corresponding conductor in another set of said conductors, and each bus bar and. the connected conductors carrying a diierent phase of power current in said system, means for transmitting current of carrier frequency through said conductors from the other of said two points to said third point, said means comprising a carrier current amplifier at said one point having its input circuit connected in shunt to one of said bus bars and its output circuit connected in shunt to another of said bus bars, said one bus bar lying in a shunt path around said input circuit and said other bus bar lying in a shunt path around said output circuit, and means in each of said shunt paths for reducing the transmission of current of carrier frequency therethrough without substantially reducing the transmission of current of power frequency, said last means each being in a portion of the respective shunt path not including any portion of said conductors carrying current of carrier frequency from said other point to said input circuit or from said output circuit to said third point, whereby said last means does not interfere with transmission of carrier current between said points.

6. A carrier current signalling system in which carrier current is transmitted over the conductors of a power distribution system, said power distribution system including two conductors extending between two spaced points, means for transmitting power frequency current readily between said conductors with substantially no potential diierence between said conductors and for impeding the ow of carrier current between said conductors, and means to transmit carrier current between said points through a circuit serially including said conductors and excluding said impeding means, said last means comprising transmitting means connected between said conductors at one of said points and receiving means connected between said conductors at the other of said points.

'7. In a carrier current signalling system, a pair of power lines extending between the same two points and each including conductors at diierent potentials of the power frequency, each of said lines including a conductor at the same potential as a corresponding conductor of the other line, means for impeding the ow of carrier current between said corresponding conductors, and means to transmit carrier current between said points overa circuit serially including said two corresponding conductors of said pair of lines and excluding said impeding means, vsaid last means comprising transmitting means connected between said corresponding conductors at one of said points and receiving means connected between said corresponding conductors at the other point.

8. In a carrier current signalling system, a pair of power lines extending between two spaced points and from one of said points to a third point, each of said lines including conductors at different potentials of the power frequency and each including a first conductor at the same potential as a corresponding first conductor of Athe other line, and a second conductor at the same potential as a corresponding second conductor or" the other line, and means to transmit carrier current between said points over a circuit serially including said two rst conductors between said two points and said two second conductors from said one point to said third point, said means comprising transmitting means connected between said rst conductors at the other of said two points, repeating means having an input circuit connected between said rst conductors at said one point and an output circuit connected between said second conductors at said one point, and receiving means connected between said second conductors at said third point.

PAUL DU MONT. 

